1. Field of the Invention
This invention relates to a formwork forming unit suitable for use in forming a concrete mold serving as a foundation of a building or the like and a method of forming such a formwork.
2. Description of the Prior Art
In forming a concrete mold serving as a foundation of a building, face plates such as composite plates or metal plates are assembled into a formwork according to the shape of a concrete mold to be formed. Thereafter, concrete is placed in the formwork and hardened. The formwork is disassembled after the concrete has been hardened. In the above-described method, the assembly and disassembly of the formwork require much labor. Further, since an amount of material to be used is increased, the transport of material costs a great deal and an amount of waste material is increased.
In view of these problems, various methods eliminating the disassembly of formwork have been proposed. For example, Japanese patent publication No. 2-178421A discloses a formwork forming unit in which wire mesh frames each of which has rough meshes and includes a steel wire frame are continuously connected to one another. A fastening wire having both ends formed with generally R-shaped engagement portions respectively is bridged between the wire mesh frames for reinforcement, so that a formwork is formed. A metal lath having fine meshes is attached to the inside of each of the wire mesh frames constituting the formwork.
When concrete is placed in the above-described formwork, a concrete mold is formed with the metal laths preventing leakage of the concrete. Since the formwork is embedded in the concrete hardened, the formwork need not be disassembled. As a result, a labor saving can be achieved.
Japanese patent publication No. 10-1952A discloses another formwork forming unit as shown in FIG. 28. A mesh such as the metal lath is welded to a metal support having rough meshes so as to cover the meshes, so that a formwork forming member 1 is formed. A plurality of formwork forming members 1 are assembled into a formwork so as to define a forming space for a concrete mold. Connecting members 2 are attached between the opposed formwork forming members 1 for reinforcement respectively and thereafter, concrete is placed in the forming space. Each connecting member 2 includes a bar-like separator 2a having both ends formed with respective male thread portions and two hook-shaped members 2b fixed to the male thread portions by nuts respectively.
In attachment of the connecting members 2, the hook-shaped member 2b is fixed to the male thread portion at one end of the separator 2a. The separator 2a is then inserted from the other end thereof through the formwork forming members 1 so as to bridge them. The hook-shaped member 2b is engaged with the support frame of one formwork forming member 1. Another hook-shaped member 2b is fixed to the male thread portion at the other end of the separator 2a with an amount of threading engagement of the nut being adjusted and is further engaged with the support frame of the other formwork forming member 1. In this construction, too, a concrete mold is formed with the mesh such as the metal lath preventing leakage of the concrete. The disassembly of the formwork is not required and the strength of the concrete mold is increased since it is reinforced by the connecting members.
The above-described formwork forming units have the following problems. In the former unit, the wire mesh frames are connected to one another and fastening wires are attached between the opposed frames, so that the formwork is formed. The metal laths then need to be attached to the inside of the formwork. As a result, the forming of the formwork requires much time. In the latter unit, when the connecting members 2 are attached to the formwork forming members 1, the amount of threading engagement of each of the nuts with the male thread portions at both ends of the separator 2a respectively needs to be adjusted so that the hook-shaped members 2b are positioned. As a result, the attachment of the connecting members 2 requires much time.